Editor’s Note: Since we made this post, the deal has sold out on JetBlue’s site.

You can book a flight for only $9 today — and you don’t have to sell your soul to some fare club overloaded with annual fees and red tape. But there is one catch.

These dirt-cheap flights won’t last. JetBlue is offering $9 flights between Boston and Newark in celebration of its new nonstop service connecting the cities, which starts May 4. But travelers have until just 11:59 p.m. Eastern Time today to get their hands on these incredibly cut-rate fares.

There’s some more fine print of which fliers should take note. Travel is only valid on Tuesdays, Wednesdays, Thursdays and Saturdays from May 4 through June 15. These fares are likely to go fast, so book as soon as possible for best availability.